The shoulder joint is a complex joint with the scapula, clavicle and the humerus all coming together to enable a wide range of movement, at least in a properly functioning joint. In a properly functioning shoulder joint the head of the humerus fits into a shallow socket in the scapula, typically referred to as the glenoid. Articulation of the shoulder joint involves movement of the humeral head in the glenoid, with the structure of the mating surfaces and surrounding tissues providing a wide range of motion.
The shoulder joint can undergo degenerative changes caused by various issues, such as rheumatoid arthritis, osteoarthritis, rotator cuff arthroplasty, vascular necrosis, or bone fracture. When severe joint damage occurs and no other means of treatment is found to be effective, a total, partial, or reverse shoulder replacement or reconstruction may be necessary. Total shoulder replacements can involve a humeral prosthetic, including a stem and a head portion used to replace the natural humeral head. Total shoulder replacements will also typically involve resurfacing of the glenoid with a prosthetic implant. The glenoid implant generally will include an articulating cup shaped to receive the prosthetic humeral head. A reversal shoulder replacement (arthroplasty) involves a different set of humeral and glenoid replacement prosthetics. In a reverse shoulder the humeral component includes a cup shaped articular surface attached to a stem implanted into the humerus, while a spherical glenoid component is used to provide an articular surface for the humeral cup.